The present invention generally relates to ophthalmic lens design and more specifically relates to junctionless ophthalmic lenses and methods for manufacturing ophthalmic lenses having junctionless, three dimensional surfaces.
Contact lens design typically involves a number of steps. The back surface, i.e. posterior surface, of the lens is frequently designed first based on the shape of the cornea and a desired cornea-lens fitting relationship. The front surface, i.e. anterior surface, of the lens is constructed to obtain the necessary refractive correction for the eye and the desired lens performance. Such performance depends on a number of factors, including, but not limited to, lens mass distribution to provide effective eyelid interaction to achieve desired lens movement and lens position, other configurational considerations to provide for the comfort of the.lens wearer and the like.
It is known that the surface topographies of a normal human cornea are often not spherical. For example, it is well known that the corneal surface of an eye has a curve that generally flattens from the center of the cornea to the periphery. A typical approach to create a flatter peripheral lens surface and adequate edge clearance between the edge of the lens and the underlying cornea/conjunctiva, has been to generate a series of conic section curves, each having a radius of curvature larger (i.e. flatter) than the preceding one. Both the anterior and posterior surfaces of conventional contact lens designs have been described in two dimensions by a series of rotationally symmetric surface segments. The surface segments may or may not be offset from the axis of symmetry.
Conventionally designed lenses have been therefor described in two dimensions, such as by a series of rotationally symmetric surface segments, and may be mathematically described thereby. The mathematical descriptions of two dimensional surface sections are made smooth and continuous by compositing, for example, splines or polynomials or blending of the sections. Such smooth, continuous surfaces can be considered to be free of junctions, or junctionless. Thus, ophthalmic lens surfaces with junctions have segments which intersect at discontinuities which can cause discomfort and/or one or more other reductions in lens performance. Thus, it is advantageous to provide an ophthalmic lens with one or more substantially junctionless surfaces.
Ducharme U.S. Pat. No. 5,452,031, which is incorporated in its entirety herein by reference, discloses a contact lens and method for manufacturing a contact lens having a smooth, junctionless surface. More specifically, the Ducharme patent discloses a method for defining the shape of the contact lens surface by relating the corneal surface to a reference curve. The reference curve may be derived from the use of piecewise polynomials and splines, based on point coordinates, resulting in a junctionless surface topography. A computer controlled lathe receives the spline data and generates a signal indicating the necessary lens form to be cut.
Vayntraub U.S. Pat. No. 5,815,237 which is incorporated in its entirety herein by reference, discloses a method for making a contact lens having a peripheral zone surface defined by an exponential function. Similarly, Vayntraub U.S. Pat. No. 5,815,236 and also incorporated in its entirety herein by reference, discloses a method for making a contact lens having a peripheral zone surface defined by a logarithmic function.
Although more closely approximating the curvature of a human eye than earlier spherically based contact lens forms, these now conventional lens computer aided design methods, which are based on using polynomial and spline based interpolations, or exponential and logarithmic mathematical functions, result in a lens constrained to a two dimensional description of the surface topography.
The surface topography of a normal human cornea is often unique and includes areas of irregularity, asymmetry and asphericity that can not adequately be described in two dimensions. Likewise the lens anterior or posterior lens surface shape required to achieve optimal lens performance cannot be adequately described in two dimensions. Particularly in such cases, conventional two dimensional computer aided lens design methods are insufficient.
Designing a lens in two dimensions is inadequate when one or more of the posterior or anterior surfaces involves an asymmetric component, that is a rotationally asymmetric component. Although computer controlled manufacturing techniques have facilitated manufacture of lenses in recent years, such techniques in practice have had only limited application and are inadequate in design and production of lenses having one or more asymmetric components, particularly lenses for use in or on an eye, such as contact lenses, intraocular lenses and corneal onlay lenses. This is because current art in lens design necessarily requires assumptions and compromises to the design by the averaging and compositing of many two dimensional surfaces. Such assumptions and compromises can result in reduced lens performance, both optically and based on user comfort.
It would be advantageous to provide new ophthalmic lenses and methods of designing and producing ophthalmic lenses which address one or more of the concerns with prior lenses, lens designs and production methods.
New ophthalmic lenses and methods for ophthalmic lens design and manufacture have been discovered. The present lenses and methods offer significant advantages over conventional lenses and methods by providing ophthalmic lenses having substantially smooth, junctionless, three dimensional surfaces which may include one or more rotationally asymmetric components. Lenses produced by the methods in accordance with the invention may include, but are not limited to, ophthalmic lenses structured and adapted for use in or on an eye, for example, all types of contact lenses, such as toric contact lenses, monofocal and multifocal contact lenses and the like intraocular lenses (IOLs), such as anterior chamber IOLs, posterior chamber IOLs and the like, corneal onlay lenses, such as lenses affixed on the cornea, lenses placed or affixed in the cornea and the like. In addition, methods of the present invention may be utilized during corneal refractive laser surgery, for example in the shaping of the cornea.
The present invention provides methods for designing and manufacturing ophthalmic lenses having one or more substantially smooth, junctionless, three dimensional surfaces, for example, wherein the surface or surfaces may have one or more asymmetrical components. The scope of the present invention also includes such lenses, tooling inserts and mold sections used to manufacture such lenses, and methods of producing such tooling inserts and mold sections.
Advantageously, the present invention provides one or more additional, for example, relative to the prior art, degrees of freedom to control lens shape, surface contour, distribution of mass, optical power location and the like parameters within the lens design. Consequently, enhanced ophthalmic lens performance, for example, related to comfort, fitting, vision and/or lens positioning are provided by the present invention.
It will be appreciated that the present methods are especially advantageous when applied to lens design where constraints of symmetry would otherwise present a disadvantage. For example, the methods are very well suited for the design of toric contact lenses, for example a toric contact lens including a posterior toric optical zone and an anterior surface shaped to provide the lens with appropriate optical power and a thickness profile facilitating lens orientation and stabilization in the form of a ballast.
Moreover, the present invention provides for enhanced reproducibility of the ophthalmic lens dimensions and surfaces. The present invention very effectively complements modern CNC lathes which have been used to produce ophthalmic lenses.
In one broad aspect of the present invention, methods for producing ophthalmic lenses are provided which generally comprise providing or specifying selected sample data points from a designated surface, for example, a designated corneal surface (the surface of the cornea of the wearer of the lens) or designated or desired anterior lens surface, interpolating between the sample data points using at least one algorithm to define a simulated three dimensional designated surface, preferably that has a relationship to, for example, is based at least in part on, the designated surface, and forming an ophthalmic lens having the simulated three dimensional designated surface. The simulated design surface preferably is sufficiently well defined, for example, in the interpolating step, to be a smooth, substantially junctionless three dimensional surface. In one embodiment, the simulated three dimensional surface is defined, during the interpolating step, using the sample data points and one or more factors or relationships for one or more lens design parameters. Advantageously, the forming step is conducted so that the ophthalmic lens has the desired lens design parameters including, but not limited to, the desired optical correction or corrections, size, configuration, space or gap between the cornea and posterior surface of the lens and other desired optical fitting relationships and the like.
Advantageously, the methods of the present invention can be used to produce contact lenses having surfaces not constrained to contours defined by a two dimensional surface of rotation. Rather, the present lenses preferably are defined by one or more smooth, substantially junctionless, three dimensional surfaces, including any rotationally asymmetric components unique or customized to the wearer""s eye. This results in an improved lens/cornea fitting relationship and/or anterior surface shape that achieve desired physical, physiological lens movement and/or vision correction objectives.
In one aspect of the invention, ophthalmic lenses are provided and comprise lens bodies, preferably structured and adapted to be located in or on an eye, having anterior surfaces and generally opposing posterior surfaces. At least one of the anterior surface and the posterior surface is a substantially smooth, junctionless, three dimensional surface. The junctionless surface may be an asymmetrical surface.
Although, for illustrative purposes, the description of the present invention set forth herein emphasizes contact lenses and methods relating to contact lenses, it is to be understood that the present invention is adapted to ophthalmic lenses in general, and preferably to ophthalmic lenses structured and adapted to be located in or on an eye, and to methods relating to such ophthalmic lenses. All such lenses and methods are included within the scope of the present invention.
The present invention may be adapted for use in producing ophthalmic lenses using any suitable processing technique or combination thereof. In one useful embodiment, the present invention is utilized in conjunction with conventional cast molding techniques, for example in the initial design of a tooling insert having a surface generally corresponding to a desired lens surface. As is well known to those skilled in the art, a tooling insert, or tool, is used to form a mold section which generally defines a negative impression of a surface of a final lens product.
For example, a tooling insert having a three dimensional, substantially junctionless surface designed by a method of the invention, is positioned in a molding apparatus, such as a molding apparatus of conventional design. A moldable composition, such as a polymeric material or a composition of a polymeric material, is introduced into the molding apparatus and subjected to conditions effective to form a mold section having a negative impression of the surface of the tool. The mold section formed by the tool may be either a back surface mold section, or a front surface mold section depending upon the tooling insert design. In other words, the surface of the tool generally corresponds to a face, either a posterior or an anterior face of the ophthalmic lens to be formed.
As is conventional, the mold section is assembled with a complementary mold section to form a lens-shaped cavity therebetween. A contact lens precursor material is introduced into the lens-shaped cavity. Upon demolding or removal from the mold sections, a lens product is obtained. As is typical, post formation processing steps may be employed to the demolded contact lens product. These steps may include hydration, sterilization, packaging and the like. These steps are well known and are not considered part of the present invention.
In accordance with the present invention, the tooling insert may include irregular or asymmetric surface contours that are customized or unique to the wearer""s eye, or contours which are not definable as a substantially junctionless surface by a two dimensional curve or interpolation. The design of the tooling insert preferably is accomplished by a method comprising providing or specifying sample data points from a designated, three dimensional surface, for example, a designated corneal surface or a designated or desired anterior lens surface, interpolating between the data points using at least one algorithm to define a simulated three dimensional designated surface, and forming the simulated three dimensional surface on the tooling insert, for example, on a tooling insert blank.
In this embodiment of the invention, cast molded ophthalmic lenses, for example, contact lenses, are made having improved fit, and/or anterior surface shape and/or vision correction performance and/or other performance relative to conventional or prior art cast molded lenses, for example, that are conventionally produced using symmetric, conic or spherical inserts.
Alternative lens manufacturing techniques may be used in conjunction with the methods of the present invention. For example, the algorithm may be used in conjunction with lens surface forming tools, including but not limited to lathes or mills. The simulated designated three dimensional surface can be cut directly onto a lens blank, for example, using a computer driven surface cutting tool.
In another aspect of the present invention, methods for reshaping corneas are provided. Such methods comprise providing or specifying sample data points from a three dimensional corrected corneal surface, that is a corneal surface to be provided to the cornea of a patient to obtain a desired result, such as a desired vision correction; interpolating between the sample data points using at least one algorithm to produce a smooth, substantially junctionless, simulated three dimensional surface; and providing an optical correction to a cornea by shaping the surface of the cornea to approximate the simulated three dimensional surface. In one useful embodiment, the methods further comprise providing sample data points from a three dimensional surface of the uncorrected surface of the cornea of the patient; and interpolating between the sample data points using at least one algorithm to produce a smooth, substantially junctionless, simulated three dimensional uncorrected surface, which is then employed in the providing step.
The present methods are effective to determine what degree of corneal reshaping is required to achieve a desired vision correction. The simulated three dimensional corrected corneal surface is the surface which will provide the desired correction, for example, vision correction. The uncorrected surface that is interpolated from the sample data points of the uncorrected cornea represents the surface of the cornea prior to reshaping. Thus, the degree of reshaping required to go from the original, uncorrected shape of the cornea to the desired or corrected shape of the cornea for a desired correction is determined.
The reshaping itself can be performed using any suitable method which can be adapted to be controlled in accordance with the present invention. In one particularly useful embodiment, the step of providing a correction includes ablating the surface of the cornea using a computer-driven laser system, such as is conventionally used in reshaping corneal surfaces. The step of providing a correction may include producing an asymmetrical surface on a corneal surface, for example, on a symmetrical corneal surface.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.